I am by no means a certified installer but I can tell you from personal experience that tap water can and will leave water spots in coatings. I had another brand's coating on my previous vehicle and had used some warm tap water to heal a small swirl mark in my Xpel paint protection film. Not wanting to wipe off water on a dirty surface I left it there like a fool not thinking it would do anything. It didn't hurt the film, but the coating on the paint sure enough had water spots in it the next time I washed it. Was I frustrated? Sure was! But it was frustration towards myself. I was the one who did it knowing full well we have harder than average water here. It was totally in no way the coating and I went ahead and reapplied it to that area.
My point here is, even though it's frustrating that this happened, it's not the coating that did it. And if it states that water spots are not covered then it's been fairly put out there in the open and not hidden whatsoever.
I have always found OPT to be a very upfront and honest company and have used their products and knowledge shared by people such as Yvan for years. I honestly feel that regardless of the brand of coating, you would have run into this same situation.
If I may, I would suggest to get it fixed and then have Mike do your maintenance. You have quite a nice car and seem to really care for it so why not let him keep it looking it's best since he does a great job as you said?
At any rate, I hope you can get this fixed and I'm sure you will enjoy your Opti-Coat Pro+ for many years to come.